Incorrect return type when using [Array.prototype.map] + [callback function with overloaded signature and using shorthand]

[maple5233]

Bug Report

🔎 Search Terms

is:issue array callback function overload

🕗 Version & Regression Information

• This is a crash
• This changed between versions ? and 4.6.2
• This is the behavior in every version I tried, and I reviewed the FAQ for entries about overload
• I was unable to test this on prior versions because it is the latest version

⏯ Playground Link

Playground link with relevant code

💻 Code

interface Animal {
  name: string
}
interface Cat extends Animal {
  sound: string
}

function handleAnimal(animal: Cat): Cat
function handleAnimal(animal: Animal): Animal
function handleAnimal(animal: Cat | Animal) {
  if ('sound' in animal) {
    return animal
  }
  return animal
}

declare let cat0: Cat

// when use in Array.prototype.map with shorthand callback, it is not ok
// typeof list2 will be Animal[]
const list = [cat0].map(handleAnimal)

// when use in Array.prototype.map with not-shorthand callback, it is ok
// typeof list2 will be Cat[]
const list2 = [cat0].map((catItem) => {
  const cat = handleAnimal(catItem)
  return cat
})

🙁 Actual behavior

const list = [cat0].map(handleAnimal) // type of list:  Animal[]

🙂 Expected behavior

const list = [cat0].map(handleAnimal) // type of list:  Cat[]

[MartinJohns]

Duplicate of #47571. Used search terms: array map overload in:title

[typescript-bot]

This issue has been marked as a 'Duplicate' and has seen no recent activity. It has been automatically closed for house-keeping purposes.